The field of art to which this invention pertains is thermosetting acrylic copolymers.
Thermosetting acrylic copolymer compositions have been used for a number of years in many industrial coating systems, particularly, in automotive and industrial coatings. Such compositions, basically, are copolymers of hydroxyalkyl acrylates or methacrylates, copolymerizable acids, and acrylic esters, methacrylic esters and/or alkenyl aromatic hydrocarbons These copolymers are then formulated with crosslinking agents, e.g., aminoplast resins, polyisocyanates, and epoxy resins, into automotive and industrial coatings. Thermosetting acrylic compositions have been described in such patents as U.S. Pat. Nos. 3,375,227, 3,438,800, 3,446,769, 3,639,147 and 4,591,533.
Many attempts have been made over the years to improve the application properties of paints made from thermosetting acrylic copolymers and the resistance properties of the paint. Other attempts have been made to raise the solids content of the formulated paint, thereby reducing the amount of environmentally undesirable solvents which must be disposed of when the paints are applied.
U.S. Pat. No. 4,609,717 discloses high solids coating compositions made from acrylic copolymer crosslinking agents and reactive diluents made from long chain aliphatic diols reacted with lactones, epoxides, or mixtures thereof.
In U.S. Pat. No. 4,681,815, coating compositions made from acrylic resins and polyester oligomers are described.
Low temperature curable coating compositions made from a solution of an alkoxymethylmelamine and a styrene-allyl alcohol copolymer added to an acrylic resin are described in U.S. Pat. No. 4,554,319.
Esters of citric acid having uses as plasticizers, stabilizers and lubricants are described in such patents as U.S. Pat. Nos. 2,122,716, 3,239,555, 3,241,992, 3,251,792 and 4,287,741 as well as German DE No. 2,306,744 and British No. 1,450,273.